Motor fuel



United States Patent Ofilice Patented July 28, 1959 MOTQR FUEL John P. Pellegrini, Jr., Blawn'ox, and Helen I. Thayer,

Pittsburgh, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa, a corporation of Delaware No Drawing. Application July 21, 1955 Serial No. 523,627

4 Claims. (CI. 4456) the operation of a gasoline engine high-compression ratios are desired. As a result, several automobile manufacturers have increased the compression ratios of their spark ignition engines to 8.5 :1 and even as high as 9:1, the future trend of the automotive industry indicating that substantially all engines will be operating at such high-compression ratios in the foreseeable future. In order to obtain smooth engine operation at these highcompression ratios it has been necessary to employ a fuel having a high octane number. To obtain a high octane number most fuels require the addition of an anti-knock agent such as. tetraethyl lead. While the addition of tetraethyl lead to gasoline improves its octane number the resulting fuel has certain disadvantages arising from the presence of the lead. One of the chief objections to the use of leaded gasolines arises from the tendency of the fuel upon being burned to form decomposition products of lead which products are deposited on the walls of the combustion chambers of the engine and on the electrodes and insulators of the spark plugs, thus reducing the efficiency of the engine and olfsetting to some extent the increased efliciency obtained by the high compression ratios. The net effect of these deposits is that the octane number requirement of the engine gradually increases as the engine is operated until some equilibrium octane number requirement is reached. The equilibrium octane number requirement of some engines which have been in operation for one hundred or more hours may be ten to fifteen numbers higher than the octane number requirement of the same engines at the start of their operation.

In an attempt to overcome the detrimental effect of the deposits of lead decomposition products in an engine, various scavenging agentshave been added to the fuel to change the form of the lead decomposition products to those which are more volatile and thus less likely to be deposited within the engine. For example, various volatile alkyl halides such as ethylene dibromide and/or ethylene dichloride have been used with tetraethyl lead to produce the corresponding halides of lead which are more volatile than the oxides. The volatile alkyl halides, however, have not completely overcome the deposition of the decomposition products. The decomposition products comprise various salts including the oxides, sulfates, bromides and chlorides of lead. These decomposition salts deposited within the combustion chamber of the engine have been found to alter adversely the engine characteristics. The adverse effect encountered as a result of the deposits of the decomposition salts is frequently evidenced by engine knocking. The knocking thus encountered is that associated with preignition of the fuel in the combustion chamber of a spark ignition engine. This knocking associated with preignition should not be confused with knocking due to explosive autoignition of the unburned portion ofthe fuel-air mixture to be traversed by the normal flame from the spark plug.

We have discovered that a motor fuel, and particularly a gasoline to which a mixture consisting of tetraethyl lead and an ethylene halide has been added in an amount normally tending to cause preignition ofsaid gasoline in the combustion chamber of a high-compression, spark ignition engine, can be improved with respect to its tendency to preignite in said engine by incorporating in said gasoline a small amount of each of (a) an organic phosphorus compound having the structural formula:

where X is selected from the group consisting of OR, N(R) ON(R) NHN(R) and SN(R) R is selected from the group consisting of alkyl, aryl, alkaryl, aralkyl, cycloalkyl, heterocyclic groups and hydrogen; and n is an integer from 0 to 3; and (b) an alkoxy compound having the structural formula:

where R and R" are alkyl groups containing between about 1 and about 10 carbon atoms and R' is selected from the class consisting of hydrogen, alkyl, haloalkyl, and alkoxyalkyl groups wherein each of the alkyl radicals contains between about 1 and about 10 carbon atoms.

The optimum amounts of the organic phosphorus compound and the alkoxy compound may vary depending upon the particular gasoline to which they are added and the engine in which the gasoline is used. The constituents are present in the gasoline in an amount sufficient to produce a motor fuel which when burned in the combustion chamber of a high-compression, spark ignition engine will give preignition free operation for a period longer than the sum of the preignition free periods of two motor fuels produced by incorporating each of the constituents in separate portions of the same gasoline.

The X groups in the organic phosphorus compounds can be unsubstituted or can contain one or more substituents which do not so affect the properties of the compounds as to render them unsuitable for use as gasoline additives, considering particularly the gasoline solubility of the compounds. Accordingly, when the various X groups are referred to herein and in the claims, the substituted as well as the unsubstituted groups are intended unless otherwise indicated. Examples of suitable substituents are the halogens, particularly chlorine and bromine; alkoxy; aryloxy; cycloalkoxy; amino; hydroxyl; cyano; mercapto; carboxy; alkanoyl; and aroyl groups.

Specific examples of the radicals which we intend to include with respect to the organic phosphorus compounds are as follows:

I. Where R is alkyl: Methyl; ethyl; propyl; isopropyl; butyl; sec-butyl; amyl; hexyl; heptyl; octyl; nonyl; decyl; undecyl; dodecyl; tridecyl; tetradecyl; pentadecyl; hexadecyl; heptadecyl; octadecyl; and the like.

II. Where R is aryl: Phenyl; l-naphthyl; Z-naphthyl; and the like.

, III. Where R is alkaryl: o, m-, p-tolyl; o, m-, p-xylyl; methylnaphthyl; dimethylnaphthyl; tri-, tetra-, penta, hexa-, heptamethylnaphthyl; 0-, m-, p-ethylphenyl; o, m-, p-propylphenyl; o, m-, p-butylphenyl; o, m-, p-amylphenyl; o, m, p-hexylphenyl; o, m-, p-heptylphenyl; o, m-, p-octylphenyl; diethylphenyl; dipropyl-, dibutyl-, diamyl-, dihexyl-, diheptyl-, dioctylphenyl; trialkylphenyl; tetraalkylphenyl; pentaalkylphenyl; indenyl; and the like.

IV. Where R is aralkyl: Benzyl; phenethyl; gammaphenylpropyl; .naphthaleneethyl; o, m-, p-methylbenzyl;

3 m-, p-methylpheenthyl; and other alkylbenzyls; 0-, m-, p-alkylnaphthaleneethyl; and the like.

V. Where R is cycloalkyl': Cyclopentyl; cyclohexyl; cyclooctyl; alkylcycloalkyl; tetrahydronaphthyl; decahydronaththyl; indanyl; and the like.

VI; Where R is heterocyclic: Pyridyl; pyrryl; thienyl; thenyl; and the like.

While all the compounds designated by the above structural formula can be used to produce a motor fuel having improved preignition characteristics, it will be understood, of course, that their effectiveness may vary.

The R groups in the organic phosphoruscompounds can be either alike or difierent, with the exception that when R is hydrogen, we prefer from the'standpoint of solubility of the compound in gasoline to have at least one other R selected from the group consisting of alkyl, aryl, alkaryl, aralkyl, cycloalkyl and heterocyclic groups. For instance, one of the R groups can be an alkyl radical, another R can be an aryl radical, another R-can be hydrogen, and the remaining R groups can be still difierent. It is preferred, however, to employ those compounds where the R groups are of the same kind except, as noted above, where R is hydrogen. whilecompounds wherein at least one of the R groups is hydrogen are desirable from the standpoint of molecular weight, the compounds wherein at least one of the R groups is a hydrocarbon radical or a heterocyclic group can be more easily incorporated into the gasoline.

Organic phosphorus compounds wherein X is OR or N(R) are particularly advantageous for use in motor fuels according to our invention. When the X group is OR, the R radical is advantageously an alkyl or an alkaryl radical. An excellent compound of this general type is tricresyl phosphate. When the X group. is N(R) the radical is advantageously an alkyl radical. The nitrogen-containing compounds can contain an R group which is a long-chain alkyl radical such as octyl, nonyl, decyl, octadecyl, and the like. For economic reasons, we prefer to use those alkyl-phosphoramides wherein the alkyl radical contains from 1 to 4 carbon atoms. For example, We prefer to employ the methyl, ethyl, propyl and butyl phosphoramides. An excellent compound of this general type is hexamethylphosphoramide.

Hexamethylphosphoramide is an example of a compound where, in the above structural formula, n is 0 X is N(R) and R is methyl. Other compounds within the above structural formula where n is 0 to 3, X is N(R) and R is. selected from the group consisting of alkyl, aryl, alkaryl, aralkyl, oycloalkyl, alkoxyalkyl, aminoalkyl, hydroxyalkyl, alkoxyaryl, aminoaryl, hydroxyaryl, haloalkyl, haloaryl, heterocyclic groups and hydrogen are hexaethylphosphoramide; hexapropylphosphoramide; hexabutylphosphoramide; N,N',N trimethylphosphoramide; N,N,N"-triethylphosphoramide; N,N,N-triisopropylphosphorarnide; N,N dicyclohexyl N,N,N",N" tetramethylphosphoramide; N,N',N-tribenzylphosphor armde; N,N-dimethyl-N,N,N",N"-tetraphenylphosphor amide; N-methyl-N-alpha-naphthylphosphoramide; N,N- b1s(2,4:dirnethylphenyl) N,N diethylphosphoramide; N,II-d1buty1-N-(2 chloro methylphenyl)phosphoramide; N,N,N" tris (2 chloroethyl)phosphoramide; N-1soamyl-N,Ndiphenylphosphoramide; N-octadecyl- N',N,N,N"-tetramethylphosphoramide; hexa(2-chloroethy1)phosphoramide; N,N,N"-tri(2-pyridyl)phosphoramide; hexathenylphosphoramide; N,N,N"-tris(2-chloro- 4 ammo 5 amylphenyl) N,N,N triethylphosphoramide; N,N,N"-trinaphthobenzylphosphoramide; phosphoryl tripiperidide; phosphoryl trimorpholide; hexa- (p-chlorobenzyl)phosphoramide; hexa(2-chloro5-t-butyl- .phenyDphosphoramide; N,N'N"trimethyl-N,N,N-tributylphosphoramide; N,N,N"-triphenyl-N,NN-triethylphosphoramide; and N,N,N"-tri(2-pyridyl)-N,N',N"-trimethylphosphoramide; N-dodecyl-N,N"-dimethylphosphorarnide; N,N,N"-tri (o-tolyl)phosphoramide; N-(S-indanyl) N',N" dibutylphosphoramide; N,N di(alphanaphthyDphosphoramide; N-benzyl-N-cyclopentyl-N"- octylphosphoramide; N,NN" tri(2-hyd.roxyethyl)phosphoramide; N,N-di(p methoxyphenyl)phosphorarnide; hexa(Z-chloropropyl)phosphorarnide; N-(4-bromophenyl) N (2,4-dichlorophenyl) N (3-thienyl) phosphoramide; N,N-dibutyl-N"-(Z-chloro-S-hydroxyphenyl)-phosphoramide; N,N-dibutyl-N"-(2-chloro-5-methoxyphenyl) phosphoramide; N (5-methoxy-l-tetralyl)- N,N',N",N"-tetramethylphosphoramide; N,N',N"-tris- (2 hydroxy 4-arnino 5 amylphenyl) N ,N,N" triethylphosphoramide; and hexa(Z-hydroxy-S-t-butylpheny1)phosphoramide.

The following list of componds illustrates various types of compounds where n is 0; and R is selected from the group consisting of alkyl, aryl, alkaryl, aralkyl, cycloalkyl, alkoxyalk-yl, aminoalkyl, hydroxyalkyl, alkoxyaryl, aminoaryl, hydroxyaryl, haloalkyl, haloaryl, heterocyclic groups and hydrogen: 7 V

I. Where X is OR: Triethyl phosphate; triisopropyl phosphate; tributyl phosphate; trioctyl phosphate; triphenyl phosphate; tricresyl phosphate; trixylyl phosphate;

- tribenzyl phosphate; trinaphthyl phosphate; tricyclohexyl phosphate; trimethoxyethylphosphate; triaminoethyl phosphate, trihydroxyethyl phosphate; trimethoxyphenyl phosphate; triaminophenyl phosphate; trihydroxyphenyl phosphate; trichlorobutyl phosphate; tri(2,4'-dichlorophenyl) phosphate; tripyridyl phosphate; tripyrryl phosphate, trithienyl phosphate; and trithenyl phosphate.

II. Where X is ON(R) N,N-diamyl-N'-phenyl-N- (4-butylphenyl)-ammonium phosphate; N-benzyl-N-cyclohexyl N-(Z-hydroxyethyl)ammonium phosphate; 4- hydroxynaphthylammonium phosphate; tris[(S-chlorobutyDammonium] phosphate; N-(2,4-dichlor0phenyl)- N'-pyridylammonium phosphate; tri(ethylammonium) phosphate; tri(triethylarnmonium) phosphate; N-phenyl- N'-(m-tolyl)-N",N"-dibenzylarmnonium phosphate; tri- (cyclopentylammonium) phosphate; tris[tri(2-hydroxyethyl) ammonium] phosphate; tri(2-aminophenylammonium) phosphate; tris[tri(2-chloroethyl)ammoniumlphosphate; tri(2-ch loroanilinium) phosphate; tripyridinium phosphate; tri(N,N-dimethyl-N-pyridylammonium) phosphate; tri(tetramethylammonium) phosphate; tris(N,N,N- trimethylaniliniurn) phosphate; tris[N,N,N-triethyl(2 ethylanilinium)] phosphate; tris (N naphthaleneethyl- N,N,N-trimethylammonium) phosphate; tris(N-cyclohexyl-N,N-dimethyl-N-ethylammonium) phosphate; tris [N,N,N tri(2 hydroxyethyl) -N ethylammonium] phosphate tris[N (2 ethoxynaphthyl) N,N,N trimethylammonitun] phosphate; tris[N-(2-chloropropyl)- N,N,N-triethylammoniurn] phosphate; tris[N-(4 -bromophenyl)-N,N,N-trimethylammonium] phosphate; and tris [N-(Z-pyridyl)-N-,N,N-trimethylammonium] phosphate.

HI. Where X is NHN(R) Hexabutylphosphorhydrazide; sym-(4-ethylphenyl)phenethylphenyl phosphorhydrazide; sym (2 butoxyphenyl)(3 hydroxybutyl) (1 -indanyl) phosphorhydrazide; and sym (4 chlorodecyl) pentachlorophenyl (2 thienyl) phosphorhydrazide.

IV. Where X is SN(R) S,S,Stris (N,N-diethylammonium) trithiophosphate; S-(N,N-dimethyl)-S-(N- ethyl) S (N" methyl N" phenyl) ammonium trithiophosphate; S,S,S tripiperdiniurn trithiophosphate; S (N chloroethyl N methyl) S (N,N diethyl)- S" (N" alphanaphthyl N propyl) ammonium trithiophosphate; S,S-,S"-triammonium trithiophosphate; S- (N-2,4-dimethylphenyl) S (N' ethyl) S" (N"- betanaphthyDamrnonium trithiophosphate; S-(N-3-hydroxypropyl) S (N' phenethyl) -S" (N" alphatetralyl)arnmonium trithiophosphate; S-(N-2-bromopropyl) S (N 2 chloromethylphenyl) S" (N- 2 hydroxy 4 methylphenyl) ammonium trithiophosphate; S,S,S tri (2 pyridylammonium) trithiophosphate; S (N,N diethyl N heptyl) S (N'- 4 isooctylphenyl) S" (N" 9 phenanthryl)ammonium trithiophosphate; S [N,N di(hydroxyethyl)l- S [N' methyl N (2 methylphenethyl) N- propyl] S" [N '7 methyl N"(methylcyclohexyl)ammonium] trithiophosphate; S [N,N,N tri (2 chloroethyl)] S [N' (2 chloro 4 methylphenyl)]- S" EN" (4 hydroxyphenyl)ammoniumltrithiophosphate; S,S',S trilIN,N dimethyl N (2 pyridyl) ammonium] trithiophosphate; S,S,S" tri (tetrapropylammonium) trithiophosphate; S,S",S" tris[N (2- naphthyl) N,N,N trimethylammonium] trithiophosphate; S,S',S" tris (N,N,N trimethylanilinium) trithiophosphate; S,S,S" tris(N benzyl N,N,N -triethylammonium) trithiophosphate; S,S,S" tris(N cyclohexyl N,N,N trimethylammonium) trithiophosphate; S,S'S" tris[N,N,N tri(2 hydroxypropyl) N- methylammonium]trithiophosphate; S,S,S" -tris[N (2- hydroxyphenyl) N,N,N trimethylammonium] trithiophosphate; S,SS" tris[N ethyl N,N,N tri (2- bromoethyl)ammoniumltrithiophosphate; S,S,S" tris [N (2,3,4 trichlorophenyl) N,N,N trimethylammonium] trithiophosphate; and S,S',S" tris[N (3- thienyl) N,N,N trimethylammonium] trithiophosphate.

Examples of compounds within the structural formula:

I. Where n is 1: Tetraethyl pyrophosphate; octamethylpyrophosphoramide; N,N di (2 -bromoethyl) N',N- dipropyl pyrophosphoramide; -N (2 chloroanilinium) N,N,N"' tri(dimethylamido) pyrophosphate; and N-(4-hydroxy-anilinium) S (N,N',N trimethylammonium)-N",N'-di-piperido thiopyrophosphate.

II. Where n is 2: Pentaethyl triphosphate; decaethyl triphosphoramide; N,N',N",N"',N"" pentapyradinium triphosphate; N,N',N tri(diethylammonium) N', N"" dihydrazidotriphosphate; and S (N cyclohexylammonium) N',N",N",N" tetra(2 chloroethyl amido) thiotriphosphate.

III. Where n is 3: Hexaethyl tetraphosphate; dodecapropyl tetraphosphoramide; hexa(4 chloroanilinium) tetraphosphate; N,N,N",N tetrabenzylammonium- N,N di(dipropylamido) tetraphosphate; and symhexamethyl tetraphosphorhydrazide.

The amount of the compound required to impart improved preignition characteristics to the fuel depends upon the particular fuel encountered, as well as the particular compound which is selected. In general, the amount is based upon that which is theoretically required to convert the lead introduced into the fuel in the form of tetraethyl lead to lead orthophosphate. While improved results can be obtained with very small amounts, amounts corresponding to at least about 0.1 times that theoretically required are preferred. Especially good results are obtained by the use of at least about 0.2 times the theoretical amount required. In general, it is not necessary to employ more than 1.5 times the amount theoretically required. Amounts greater than 1.5 times the theoretical amount can be employed, but for economic reasons, we prefer to use only the amount required to give the desired improvement. Therefore, we prefer to employ an amount equal to about 0.2 to about 1.5 times that theoretically required to convert the lead to lead orthophosphate. In view of the fact that the amount of tetraethyl lead in the gasoline varies from one fuel to another, it is difiicult to state on a weight basis the amount of a particular compound based upon the weight of the gasoline. However, once knowing the amount of tetraethyl lead present in the gasoline, it is an easy matter to calculate the amount of the particular compound required. Most gasolines on the market today contain up to about three cubic centimeters of tetraethyl lead per gallon of gasoline. Based upon fuels containing up to about three cubic centimeters of tetraethyl lead, we have determined that the amount of the compound required in accordance with our invention is between about 0.001 and about 4.0 percent by weight based on the weight of the gasoline. It will be understood, of course, that the optimum amount on a weight basis for one particular compound may not be the optimum amount for another compound. One reason for this is that the eilectiveness of the compounds varies from one compound to another. Another reason is that the molecular weight of one compound may be twice the molecular weight of another compound, so that to get an equivalent amount of phosphorus when using the compound having the greater molecular weight, one is required to use twice the amount of compound on a weight basis. 'Of course, when the compound is a polyphosphorus compound, such as octamethylpyrophosphoramide, decamethyltriphosphoramide, dodecamethyltetraphosphoramide, tetra(ethylammonium) pyrophosphate, tetramethylpyrophosphorhydrazide, or the like, the amount by weight may be less because of the additional phosphorus in the compound. For instance, while tricresyl phosphate and hexamethylphospho ramide have only one available phosphorus per molecule, hexaethyl tetraphosphate have four available phosphorus atoms. In any event, the amount of the organic phosphorus compound used is sufficient to give marked improvement when combined with the alkoxy compound.

Specific examplesof some of the alkoxy compounds which can be used in accordance with ourinvention are methylal, acetal, n-propylal, isopropylal, dimethyl chloroacetal, the dimethyl acetal of octaldehyde, 1,1,3,3-tetraethoxypropane and the polymethoxyacetals. The alkoxy compounds are available commercially and thus their preparation constitutes no part of this invention. The lower molecular weight alkoxy compounds such as methylal, acetal, propylals, and the like can be prepared by the partial oxidation of the corresponding alcohol at low temperature in the presence of an acid oxidizing agent.

The amount of the alkoxy compound which is incorporated in the fuel depends upon the amount of tetraethyl lead in the fuel, as well as the particular alkoxy compound which is selected. In general, good results can be obtained when the molecular ratio of alkoXy compound to tetraethyl lead is about 1:1 to about 10: 1. The optimum ratio of alkoxy compound to tetraethyl lead will vary With the compound. For example, we have found that in the case of a bifunctional acetal (l,1,3,3-tetraethoxypropane) improved engine operation with respectto preignition can be obtained when the molecular ratio of the bifunctional acetal to tetraethyl lead is at least about 2:1. In the case of a monofunctional acetal, such as dimethylacetal of octaldehyde, improved engine operation with respect to preignition can be obtained only when the ratio of the monofunctional acetal to tetraethyl lead is at least about 4: 1.

In view of the fact that the amount of tetraethyl lead in the gasoline varies from one fuel to another, and also in further view of the fact that the molecular weight of the alkoxy compounds is difierent for each of the various compounds, it is difiicult to state on a weight basis the amount of the alkoxy compounds to be added to the gasoline based upon the weight of the gasoline. However, once knowing the amount of tetraethyl lead present in the gasoline the amount of the alkoxy compound required can be readily calculated by converting the amounts by weight to mols. Based upon fuels containing 3 cubic centimeters of tetraethyl lead per gallon of gasoline, we have determined that the amount of methylal required to give a molecular ratio of methylal to tetraethyl lead between about 1:1 and 10:1 is about 0.042 to about 0.42 percent by weight, respectively, based on the weight of a 60 API gravity gasoline. It will be understood, of course, that when commercially available products are used the optimum amount of product on a weight basis will vary depending upon the purity of the product. If, for instance, a commercially available anti-knock mixture comprising tetraethyl lead and ethylene halides is used the percent by weight of the alkoxy compound will and dodecamethyltetraphosphoramide be less than if substantially pure tetraethyl lead is used.

For example, if 3 cubic centimeters of a tetraethyl lead.

mixture comprising 61.5 percent by weight of tetraethyl lead is used the amount of methylal required in one gallon of a. 60 API gravity gasoline would correspond to about 0.025 to about 0.25 percent by weight. Likewise, if a commercially available methylal is used which contains a small amount of inert impurities the weight percent of commercial mixture employed will be greater than the weight percent of pure methylal.

. The motor fuel to which the organic phosphorus compound and the alkoxy compound is added can comprise a mixture of hydrocarbons boiling in the gasoline boiling range. However, the problem resulting from the formation of lead deposits is primarily present in heavily leaded gasoline having a Research octane number of at least about 90. The gasoline to which the tetraethyl lead is added can be either a straight-run gasoline or a gasoline obtained from a conventional cracking process, or mixtures thereof. The gasoline to which the organic phosphorus compound and the alkoxy compound is added, in accordance with our invention, can also contain components obtained from processes other than cracking, such as alkylation, isomerization, hydrogenation, polymerization, hydrodesulfurization, hydroforming, Platforming," or combinations of two or more of such processes, as Well as synthetic gasoline obtained from the Fischer-Tropsch and related processes.

In addition to the organic phosphorus compound and the alkoxy compound, the leaded gasoline of our invention can contain other conventional additive agents including upper cylinder lubricants, oxidation inhibitors, anti-freeze agents, metal deactivators, dyes, and the like.

The alkoxy compounds and the organic phosphorus compounds present no particular problem with respect to their addition to gasoline. While the compounds can be added directly to the gasoline, one convenient method of adding them to the fuel is to form a concentrate thereof with a liquid hydrocarbon solvent and thereafter adding the concentrate to the fuel. Any solvent which does not adversely affect the desirable properties of the fuel can be used. One concentrate which can be used for the purpose of our invention consists of about 7.50 percent by weight of organic phosphorus compound, about 70.0 percent by weight of alkoxy compound and about 22.5 percent by weight of toluene. The concentrate can, of course, contain other conventional gasoline additives, if desired.

Thus a gasoline benefiting concentrate can be formed by admixing an organo-metallic anti-knock composition with a mixture of the organic phosphorus compound and the alkoxy compound. In such instances, a mutual solvent may be desirable. When such gasoline benefiting concentrates are prepared they can, of course, contain other additive agents such as an oxidation inhibitor, an anti-freeze agent, a metal deactivator, an upper cylinder lubricant, a lead scavenging agent, a dye, and the like. Since the amount of the organic phosphorus compound and the alkoxy compound depends to some extent upon the amount of the tetraethyl lead present this method of adding the compounds to the gasoline serves as a convenient way of adding the correct amount of organic phosphorus compound and alkoxy compound to unleaded fuels. Thus, a gasoline benefiting concentrate can be made by admixing tetraethyl lead or commercially available mixtures of tetraethyl lead with the organic phosphorus compound and the alkoxy compound. Such concentrates advantageously contain volatile alkyl halides. A gasoline benefiting concentrate can thus be made by admixing tetraethyl lead and a halide of ethylene with an organic phosphorus compound wherein the phosphorus compound is present in an amount between about 0.1 and 1.5 times the theoretical amount required to convert the lead to lead phosphate and an alkoxy compound wherein the molecular ratio of alkoxy compound to tetraethyl lead is about 1*:1ito about 10:1.

One convenientmethod of preparing a gasoline benefi ing concentrate is to start with a commercially available concentrate comprising tetraethyl lead and the halides of ethylene. One such commercially available product consists of about 61.5 percent by weight of tetraethyl lead, about 17.9 percent by weight of ethylene dibromide and about 18.8 percent by weight of ethylene dichloride. This commercially available concentrate has a specific gravity of 1.587 at 20 C. The amount of the gasoline benefiting concentrate added to gasoline will vary depending upon the desired octane number of the gasoline. Ordinarily, the concentrate is added in an amount sumcicnt to incorporate about 1 to about 3 cubic centimeters of tetraethyl lead ina gallon of gasoline.

In order to illustrate the improved preignition characteristics obtained with afuel of the invention, a test was employed in which the fuel was burned in a stationary Cadillac engine having a 9 to l compression ratio. In this test, the engine was operated on a cycling schedule consisting of three minutes at 1500 r.p.m., road load followed by a one-minute idle at 450 rpm. At the end of each twenty-four hours under this cycling schedule, preignition determinations were made at 1000 and 2000 rpm. After the preignition determinations were made the engine was then put back on the cycling schedule. The test was continued until violent preignition was encountered for two successive periods at the same rpm. The preignition thus encountered is referred to as sustained violent preignition. The engine conditions at the time of the preignition evaluation were as follows:

11.5:1 and 10.3:1 at 1000 and 2000 rpm. respectively.

Air: fuel ratio In this test the load and throttle position are varied, dependent upon when preignition is encountered. At the start of the test the engine is under no load. The throttle is gradually increased until preignition is observed. If full throttle is reached without preignition, the engine is operated at full throttle for 30 seconds, or less if preignition occurs sooner. If preignition is not encountered after hours (5 days), the test is usually discontinued. The data set forth in Table I were obtained when a Cadillac engine was operated under the above test procedure with a reference gasoline, normally tending to preignite, containing about 2.10 ml. (3.48 grams of tetraethyl lead and about 2.07 grams of about a 50-50 mixture of ethylene dibromide and ethylene dichloride per gallon of gasoline. The comparative tests were made with separate portions of the same reference gasoline, each portion containing one or more additives as indicated. The reference gasoline employed in the tests reported in Tables I, II and III was a premium grade gasoline having a CFR Research Method octane number of about 96.

Table I Nufiilber rgfi24=houri pecriods un sue a ne vio en re- C0rnp0s1t10n. ignition was reached Reference gasoline 0.98 Reference gasoline containing 0.2 theory (0.0087 percent by weight) hexamethylphosphoramide 2.6 Reference gasoline containing 0.161 percent by weight 1,1,3,3-tetraethoxypropane 1.9

It will be noted from the data in Table I that the Cadillac engine ran for less than one 24-hour period before sustained violent preignition was encountered. When the engine was operated with a separate portion of the same reference gasoline containing 0.2 theory of hexamethylphosphoramide, sustained violent preignition was not encountered until 2.6 tWenty-four-hour periods of operation. Improved results (1.9 twenty-four-hour periods) was likewise obtained when the engine was operated with another portion of the gasoline containing 0.161 percent by weight of 1,1,3,3-tetraethoxypropane. When the test was repeated with a further portion of the gasoline containing 0.2 theory of hexamethylphosphoramide and 0.161 percent by weight of l,l,3,3-tetraethoxypropane, strikingly superior results were obtained as evidenced by the fact that the engine operated for seven twenty-four-hour periods before encountering sustained violent preignition. The results thus obtained were surprising in that the combination of additives gave preignition-free operation for a period longer than the sum of the periods obtained when using the additives separately. The improved preignition characteristics of the motor fuel of our invention is thus not a mere arithmetic summation of two separate improving agents.

The striking effect encountered when an organic phosphorus compound and an alkoxy compound are combined is further illustrated by the data in Table II.

Table 11 Number of 24-hour periods until sustained violent preignition was reached Reference gasoline containing 0.2 theory (0.0177 percent by weight) tricresyl phosphate and 0.161 percent by weight 1,l,3,3- tetraethoxypropane 1 12.6+

Molar ratio of tetraethoxypropane tetraethyl lead2 1.

The data in the above table clearly demonstrate the superior results obtained with a composition of the invention. It can be seen that the engine ran for about two twenty-four-hour periods before sustained violent preignition was encountered when operating with the reference gasoline and the reference gasoline containing 0.161 percent by weight of 1,1,3,3-tetraethoxypropane. When the engine was operated with the reference gasoline containing 0.2 theory of tricresyl phosphate, the period was extended by 100 percent to 4.1 twenty-four-hour periods. When the l,1,3,3-tetraethoxypropane and tricresyl phosphate were combined, the engine operated for more than 12.6 twenty-four hour periods.

In order to further illustrate the invention, a reference gasoline was compared with separate portions of the same gasoline containing tricresyl phosphate and methylal. The results are tabulated in Table 111.

Table 111 Number of 24-hour periods until sustained violent preignition was reached Molar ratio of methylal tetraethyl lead-4:1.

The data in Table III show that the preignition characteristics of a gasoline are hindered by the addition of methylal. When methylal and tricresyl phosphate are combined, sustained violent preignition is not encountered u for a period of time longer than the period obtained using tricresyl phosphate. Thus, not only has the hindering effect of the methylal been overcome, but also the improving elfect of the tricresyl phosphate has been enhanced. This result was indeed surprising.

While our invention is described above with reference to various specific examples and embodiments, it will be understood that the invention is not limited to such examples and embodiments and may be variously practiced within the scope of the claims hereinafter made.

We claim:

1. A motor fuel having reduced preignition tendencies consisting essentially of a gasoline containing about 1 to about 3 cubic centimeters of tetraethyl lead per gallon of gasoline; about 0.2 to about 1.5 times the theoretical amount of an organic phosphorus compound selected from the group consisting of hexamethylphosphoramide and tricresyl phosphate required to convert the lead to lead phosphate; and an alkoxy compound selected from the group consisting of methylal and l,l,3,3-tetraethoxypropane, wherein the molecular ratio of the alkoxy compound to tetraethyl lead is about 1:1 to about 10:1.

2. A motor fuel having reduced preignition tendencies consisting essentially of a gasoline containing about 1 to about 3 cubic centimeters of tetraethyl lead per gallon of gasoline; about 0.2 times the theoretical amount of hexamethylphosphoramide required to convert the lead to lead phosphate; and 1,1,3,3tetraethoxypropane, the molecular ratio of 1,1,3,3-tetraethoxypropane:tetraethyl lead being about 2:1.

3. A motor fuel having reduced preignition tendencies consisting essentially of a gasoline containing about 1 to about 3 cubic centimeters of tetraethyl lead per gallon of gasoline; about 0.2 times the theoretical amount of tricresyl phosphate required to convert the lead to lead phosphate; and 1,1,3,3-tetraethoxypropane, the molecular ratio of 1,1,3,3-tetraethoxypropane:tetraethyl lead being about 2:1.

4. A motor fuel having reduced preignition tendencies consisting essentially of a gasoline containing about 1 to about 3 cubic centimeters of tetraethyl lead per gallon of gasoline; about 0.2 times the theoretical amount of tricresyl phosphate required to convert the lead to lead phosphate; and methylal, the molecular ratio of methylahtetraethyl lead being about 4: 1.

References Cited in the file of this patent UNITED STATES PATENTS Nikaido Apr. 27, 1926 Contardi et al. Apr. 19, 1938 Thompson Sept. 29, 1942 Van Hartesveldt Feb. 27, 1951 Yust et al. Oct. 2, 1956 FOREIGN PATENTS Australia Aug. 17,

OTHER REFERENCES Chemical Abstracts, July 10, 1954, vol. 48, No. 13, col. 7886e-g. 

1. A MOTOR FUEL HAVING REDUCED PREIGNITION TENDENCIES CONSISTING ESSENTIALLY OF A GASOLINE CONTAINING ABOUT 1 TO ABOUT 3 CUBIC CENTIMETERS OF TETRAETHYL LEAD PER GALLON OF GASOLINE; ABOUT 0.2 TO ABOUT 1.5 TIMES THE THEORETICAL AMOUNT OF AN ORGANIC PHOSPHORUS COMPOUND SELECTED FROM THE GROUP CONSISTING OF HEXAMETHYLPHOSPHORAMIDE AND TRICRESYL PHOSPHATE REQUIRED TO CONVERT THE LEAD TO LEAD PHOSPHATE; AND AN ALKOXY COMPOUND SELECTED FROM THE GROUP CONSISTING OF METHYLALA AND 1,1,3,3-TETRAETHOXYPROPANE, WHEREIN THE MOLECULAR RATIO OF THE ALKOXY COMPOUND TO TETRAETHYL LEAD IS ABOUT 1:1 TO ABOUT 10:1. 